The various methods prevalent up to 1985 for analyzing mandibular kinematics were based on the use of mechanical instruments all to a greater or lesser extent derived from mandibulographs, whose commercial appearance dated from the 1950s.
Such apparatus permitted the recording of a relatively restricted expression of these kinematics, since the expression was limited to the so-called border movements of the mandible. Moreover, the interpretation of the graphs obtained by these methods gave rise to a number of errors due to the misunderstanding of the functional cycle and to the intervention of mechanical processes which led to the existence of artifacts in the graphs.
Another negative aspect of such apparatus is the considerable space taken up in the oral cavity in cumbersome and bulky fixation procedures with which it was impossible to envisage the recording of a normal physiology of the said kinematics.
The use of apparatuses employing a recording system, which occupies little space in the oral cavity and does not in any way interfere with the masticating cycle, nowadays permits the straightforward recording of the functional kinematics which have up till now been remote from our everyday concerns.
The work carried out by Lundeen and Gibbs had already provided a first example of this with the "gnathic replicator". These studies have been added to considerably by a large number of authors, who have demonstrated the more uncertain aspects of the masticating cycles and have permitted a more exact approach to the phenomena which intervene in the cycles in term of neuromusculature, quality of the foods crushed, posture of the subject etc.
A number of other apparatuses have attempted to represent as clearly as possible the data essentially characteristic of the masticatory apparatus. Mention should be made in particular of the recent work carried out by Lewin, which has led to the production of the Siemens "sirognathograph", the "Nex K6 diagnostic system" from Myo-tronics Inc, the "LR Candylograph" from Dentron, the "stereognathograph" from Dr. Burchhardt or the Cyberhoby computer pantograph from Denar.
Finally, mention should be made of the "visitrainer" described for the first time in 1981 by the team under Professor Hobo and Professor Mori in Japan. It uses an LED (light emitting diode) fixed on the mandibular incisors. At the same period the team under Professor Hobo developed a system using a charge transfer device (CTD) as a reading means; the whole assembly is connected to various calculation elements (computer) and their associated peripherals.
These works include the principles developed by Barrie in 1967 and his "photoelectric mandibulography". 1984 saw the appearance of the first "Saphon visitrainer model 1". The latter will soon be followed by the C2 model, then the 3 (SVT) model. These models have been developed by the company Tokyo Shizaisma C.O. Ltd. and differ in particular in their ergonomic approach (weight, number of points analyzed per second, etc. . . . ).
The fact of having to move a single camera three times in order to analyze the movements in the horizontal, frontal and sagittal planes prevents these movements from being determined spatially, because a subject never moves his joints in the same manner, and this prevents any connection from being made between the three movements.
At the same period Jemt and Karlson showed that the use of two cameras and a diode fixed on the incisors could permit analysis of the mandibular movements in three dimensions. In actual fact, this is not correct. In particular, it is found that a purely rotational movement, often present in the human body, cannot be detected correctly.